The reaction of cyclopentanone ( 1 ), elemental sulfur and either malononitrile or ethyl cyanoacetate gave the cyclopenta[ b ]thiophene derivatives 3a and 3b , respectively. The reaction of either 3a or 3b with either 2a or 2b afforded the cyclopenta[4,5]thieno[2,3-b]pyridine derivatives 5 and 6 , respectively. The reactivity of the latter products toward different reagents was studied to give pyrazole, pyridine, pyrimidine derivatives. The antitumor evaluation of the newly synthesized products against the three cancer cells namely breast adenocarcinoma (MCF-7), non-small cell lung cancer (NCI-H460) and VNS cancer (SF-268) showed that some of them have high inhibitory effect towards three cell lines which is higher than the standard. Moreover, the anti-leishmanial activity of the newly synthesized products was tested on Leishmania amastigotes showed that some compounds have high activity.